The use of optical waveguides, and specifically optical fibers, has become common in sensors of all types. One important aspect of these sensors is accurately detecting the energy that exits from the optical waveguide. Several methods have been devised to detect this energy. See Paul A. Willis; Industrial Research and Development, September, 1982.
These methods of detection all have difficulties in efficient energy conversion. Light energy to electrical energy conversion is inefficient because the modes of the radiation energy exiting from the end of the optical waveguide at large angles do not permit efficient energy coupling to these photodetectors.